1. Field of the Invention
The invention relates generally to an apparatus for treating surfaces of wafer-shaped articles, such as semiconductor wafers.
2. Description of Related Art
Semiconductor wafers are subjected to various surface treatment processes such as etching, cleaning, polishing and material deposition. To accommodate such processes, a single wafer may be supported in relation to one or more treatment fluid nozzles by a chuck associated with a rotatable carrier, as is described for example in U.S. Pat. Nos. 4,903,717 and 5,513,668.
With increasing miniaturization of the devices fabricated on semiconductor wafers, processing those wafers in an oxygen-containing atmosphere becomes more problematic. For example, when wafers undergo wet processing in stations that are open to the surrounding air, the oxygen content of the air causes unwanted corrosion of copper on the front side of the wafer. More specifically, dissolved oxygen in the chemistry leads to oxidation of copper and cap layers in advanced BEOL (back-end-of-line) technologies during the liquid dispense, leading to increased copper loss by dissolution of the generated oxides of copper. Lateral material loss is especially significant to degradation of device performance.
During processing on a single wafer spinning tool in an open environment the oxygen from the air can diffuse through the liquid layer on the wafer to the wafer surface, leading to additional copper oxidation and therefore additional copper loss. This effect is enhanced where the liquid layer is very thin, e.g. at the wafer edge. This is also shown for watermark formation during drying.
Oxidation of copper due to dissolved oxygen in the chemistry can be avoided by replacing the oxygen with an inert gas such as nitrogen. Similarly, watermark formation can be mitigated by reducing the oxygen in the environment during drying on single wafer spin tools.
U.S. Pat. No. 6,807,974 describes a chamber equipped with a gas injection section for that purpose. However, the structure described in that patent does not permit processing or rinsing liquids to be dispensed on the wafer while the inert gas is being introduced by the gas injection section. The gas injection section of this patent is moreover depicted as being of greater diameter than the wafer to be treated, and forms a lid for a sealed interior chamber.
U.S. Pat. No. 6,273,104 describes an apparatus for processing a substrate in which a vertically movable blocking plate of diameter slightly less than the workpiece dispenses nitrogen downwardly onto a wafer surface and is further equipped with a central nozzle for dispensing deionized water for rinsing the workpiece. As the blocking plate is fixed in a coaxial relationship with the workpiece, the relative lateral positions of the gas nozzles and liquid nozzle to the workpiece are fixed.
A need therefore exists for wafer processing stations in which the gas atmosphere can be controlled, yet which permit performing a variety of processes on a wafer loaded in the processing module.